Graham suggested Mueller look into reports he was nearly fired in June.

Firing special counsel Robert Mueller would put an end to Donald Trump’s presidency, Sen. Lindsey Graham warned Sunday — one of several top Republicans to express support for the investigator after reports that Trump tried to get him canned.

“I’m sure that there will be an investigation around whether or not President Trump did try to fire Mr. Mueller. We know that he didn’t fire Mr. Mueller. We know that if he tried to, it would be the end of his presidency,” Graham said on ABC’s “This Week,” adding that Trump’s aides are well aware of the potential consequences.

“It’s pretty clear to me that everybody in the White House knows it would be the end of President Trump’s presidency if he fired Mr. Mueller.”

Republican lawmakers were unanimous Sunday in expressing support for keeping Mueller on the job — but split on whether Congress should pass legislation to protect him after reports that Trump months ago ordered the special counsel’s firing.

Trump backed off from the order in June only after White House counsel Donald McGahn threatened to resign rather than carry it out, The New York Times first reported.

Graham last summer introduced a bill to block Mueller from being fired while he conducts his investigation into Russian interference in the 2016 election, and the possibility of collusion between the Russians and Trump’s campaign.

“I’ll be glad to pass it tomorrow,” Graham, of South Carolina, said of the bill.

Trump, while visiting Switzerland last week, called the report "fake news."

(FABRICE COFFRINI/AFP/Getty Images)

He said Mueller should probe reports that Trump ordered his own dismissal, along with his firing of FBI Director James Comey and other actions that could suggest obstruction of justice.